Lindane (g-hexachlorocyclohexane, g-HCH) was used as an insecticide on fruit and vegetable crops, for seed treatment and in forestry. It was also used as a therapeutic pesticide in humans and animals. Several countries have restricted the use of Lindane.
Lindane can be degraded in soil under aerobic conditions; the half-life ranges from 88 to 1146 days. γ-Pentachlorocyclohexene, hexa-, penta-, tetra- and trichlorobenzenes and penta- and tetrachlorophenols are the degradation products most commonly found. Anaerobic degradation is more rapid than aerobic degradation under laboratory conditions (half-life 12–174 days). Under anaerobic conditions, the same chlorinated benzenes and hexenes are found, but not the phenols.
Leaching of Lindane to groundwater rarely occurs, and in surface waters, Lindane can be removed by evaporation. Ultraviolet light seems to transform γ-HCH into α-HCH to some extent. Bacteria also influence the isomerization of γ-HCH to α-HCH. The degradation products found in soils have also been found in water. In surface waters, Lindane can be removed by evaporation.
Exposure of humans occurs mainly via food, but this is decreasing. There may also be exposure from its use in public health and as a wood preservative.
In the absence of genotoxicity and on the basis of the weight of the evidence from the studies of carcinogenicity, JMPR has concluded that Lindane is not likely to pose a carcinogenic risk to humans. Further, in an epidemiological study designed to assess the potential association between breast cancer and exposure to chlorinated pesticides, no correlation with Lindane was found.
Toxicity to Animals
Lindane was toxic to the kidney and liver after administration orally, dermally or by inhalation in short-term and long-term studies of toxicity and reproductive toxicity in rats. The renal toxicity of Lindane was specific to male rats and was considered not to be relevant to human risk assessment, since it is a consequence of accumulation of a2u-globulin, a protein that is not found in humans.
Hepatocellular hypertrophy was observed in a number of studies in mice, rats and rabbits and was reversed only partially after recovery periods of up to 6 weeks.
Lindane did not induce a carcinogenic response in rats or dogs, but it caused an increased incidence of adenomas and carcinomas of the liver in agouti and pseudoagouti mice, but not in black or any other strains of mice in a study of the role of genetic background in the latency and incidence of tumorigenesis. Joint FAO/WHO Meeting on Pesticide Residues(JMPR) has concluded that there was no evidence of genotoxicity.
For more information:
- Submission to include Lindane in the Stockholm Convention - proposal; screening; risk profile; risk management profile
- Full description and toxicity of Lindane from the U.S. National Library of Medicine
- Health Canada Lindane Review Board
Adapted from Lindane in drinking-water. Background document for preparation of WHO Guidelines for drinking-water quality. World Health Organization (2004)